Vacuum jacketed glass tube and shape



May 31, 1.938. NI M. ELIAS 2,119,009

I VACUUM JACKETED GLASS TUBE AND SHAPE Filed June 27, 1935 2 Sheets-Sheet 1 BYZ 1 48 ATTORNEYJ N. M. ELIAS VACUUM JACKETED GLASS TUBE AND SHAPE May 31, 1 938.

2 Sheets-Sheet 2 Filed June .27, 1935 Patented May 31, was 2,119,009

. UNITED STATES PATENT OFFlCE VACUUM JACKETED GLASS TUBE AND SHAPE Nathaniel M. Elias, New York, ,N. Application June 27, 1935, Serial No. 28,633

9 Claims. (01. 49-82) This invention relates to glass tubes, especially moderate expense, this method including a' novel to the fabrication of double walled tubes and mode of evacuation by which the vacuum itself, more particularly to the provision of such tubes acting while the tube material is hot and soft, in which the intramural space constitutes a permits atmosphere pressure to become effective jacket highly evacuated to reduce heat transfer to cause a sealing contraction of the walls which therethrough, in order to produce a vacuum-insumakes unnecessary the retention of the convenlated tube or tube-shape which is transparent. tional tip. I

One of the uses to which such tubing or shapes Another object of the invention is 'to provide can be applied is in the transfer of liquids at very a method of making such tubes not only in 10 low temperatures, when some characteristic of straight forms but with curved and other shapes. 10 the liquid is to be observed optically without too Still another'object of the invention is to progreat absorption of heat by the liquid, or serious vide for the fabrication of such'vacuum jacketed frosting of the outside of the tube because of glass shapes of widely diverse character as for deposition of moisture thereon from the atmosexample,.in L's, Ts, curves, spirals, 'etc.; also phere. as sight-glasses, gauge-glasses, and feed-tubes,

Another use therefor is as a gauge glass, paretc., to be used in combination with systems for ticularly for low temperature liquids or liquefied containing and/or transferring liquefied 8 8 gases. Even at temperatures as low as 50 C., liquids at temperatures below 10 C.'; etc., as for serious frosting does not occur with the tube of example, systems containing brine, oil or liquid the present invention. Use of such glasses for food products at such low temperatures. 20 liquefied ammonia and other liquefied gases as Other objects and advantages will appear as well as for cold oil, refrigerating brine solution, the description of the particular physical embodicold creamery products, etc., has been found to be ment selected to illustrate the invention proquite practicable. gresses, and the novel features of the invention While double-walled tubes have been known, will be particularly pointed'out in the appended 25 their fabrication has been attended with numerclaims. ous difficulties, among which has been expe- In describing the invention in detail and the rlenced especially the dimculty in fabrication of particular physical embodiment selected to illussuch tubes by a method which can be practiced trate the invention, reference will be had to the commercially to make tubing in which the vacaccompanying drawings, and the several views 30 uum jacket shall include substantially the whole thereof, wherein like characters of reference length of the tube; another difliculty has been designate corresponding parts, and in which: that the double-walled tube is usually left with Fig. l is a view of somewhat diagrammatic a tip at the sealed-off end or if the tips have been character illustrating the preliminary stage in the.

removed the cost has been prohibitive; and still preferred method for fabrication of double 35 another difficulty is that there has been lacking walled, vacuum jacketed glass tubes in pursuance a practical means for compensating for the un- 0f the invention; equal expansion between the inner and outer g. 2 s 8- Simllar View 0! t t Sta e n sa d walls of the tube. method; A principal object of the invention is to pro- Fig. 3 illustratesa subsequent stage; 40 vide a method of making such double walled vac- Fig. 4 shows t e fi l p oduct resulting om uum jacket tubes by which method the vacuum the fabrication of an illustrative tube; this figure jacket is made co-extensive with the length of the being a view in side elevation, partly in section tube, and to fabricate double-walled, vacuum of adouble-walled, vacuum jacketed glass tube in jacketed tubes in which means are provided to the construction of which my invention has been 45 compensate for unequal expansion and contraccarried into effect; tion, as between the walls, especially when long Fig. 5 is a similar view of a modification; tubes are required. This provision is made, in Fig. 6 is a similar view showing another modi- -the present invention, preferably by the inclusion flcatlon;

of bulbs in either the inner or the outer tube wall Fig. 7 shows still another modification; 50 or both, which bulbs act to give resilience to the Fig. 8 shows a preliminary step in carrying the glass and avoid breakage at the joints. invention into eifect for the formation of an L- Another object is to provide a method of fabshaped tube; 4 ric'ating such glass tubes or shapes out of plural Fig. 9 illustrates in dotted lines the final stage components without any sealed-ofi tip, and at in ma ing Such 8 tube as t Of h 118- ure being a view in longitudinal section ofthe completed L-shaped tube;

Fig. 10 illustrates a preliminary step in making a tube where the outer glass envelope does not correspond exactly in shape with the inner tube;

Fig. 11 illustrates an intermediate step in the fabrication of the tube, which is shown in Fig. 12, in its final shape;

Fig. 13 is a small-scale view of somewhat diagrammatic form illustrating a vacuum jacketed sight glass made according'to my invention and assembled in combination with a condenser;

Fig. 14 illustrates the combination of a vacuum jacketed gauge glass with a storage tank containing liquids at temperatures below 10 C.;

Fig. 15 shows a series of vacuum jacketed transparent glass tubes of different shapes assembled in a system for conveying liquids at low temperatures.

The novel method of my invention may be illustrated and understood readily by reference to several steps thereof carried out in the fabricafion of the tube shown in its final form in Fig. 4, and Figs. 1, 2 and 3 serve to illustrate stages or steps in said fabrication.

These figures show particularly the fabrication of a tube which in its final form lacks the conventional sealed-oft tip which characterizes the ordinary tubes of such structure.

In making this new form of tipless jacketed tube, there is first prepared a tube 20 such as that shown in Fig. 1, which has a straight portion 2|, closed at one end by a bulb 22 and having its other end left open as at 23. The tube is shown partially in section to reveal the inner wall structure.

The next step in the method consists in sealing to the tube 20 an outer tube, at the open end 23, as shown in Fig. 2, this outer tube being designated generally 24, its walls being substantially parallel with those of the tube 20 throughout the length of the tube, except at the region of the bulb 22, where the walls, as at 25, approach very closelyto' the periphery of the bulb 22. Beyond that region, the extremity-23,013 the outer ,tube may be drawn in to form a neck of convenient dimensions for attachment of a known or suitable evacuating means.

The next step in the fabrication of this form of tube involves a very important feature of the present invention, in that after a vacuum has been created by evacuation through the neck, and preferably after a preliminary sealing at the region designated 26, the walls 25 of the outer tube are suitably heated so that the vacuum exercises a constrictive efl'ect, or, to be more accurate, the inner support of the walls is so diminished that atmospheric pressure results in bringing the outer walls 25 into contact with the bulb 22, and the inner and outer walls become fused together as shown very clearly at the annular region .21 in Fig. 3.

The final step consists in cutting oil the surplus tip 28, at a transverse plane so disposed that the thickness of the end wall at the region indicated at 29 in Fig. 4 is approximately that of the inner wall 30 and of the outer wall 3| of the tube in its completed shape as shown in Fig. 4. Some further fusing or molding may be necessary to give a good finish, as will be understood by those skilled in the art, the whole glass being preferably annealed very carefully to relieve internal tension in the material.

The product, as shown in Fig. 4, is a doublewalled glass tube, vacuum jacketed, and having no sealed-off tip at either end, so that the vacuum jacket is substantially co-extensive in length with the length of the tube.

In experimenting with tubes of this novel structure, I have found that for many purposes the annular space between the two tube walls may be less than one-quarter of an inch, and still be effective for thepurpose described. Such a dimension is not however necessary, and the annular space may be either greater or less according to the exigencies of particular embodiments. The dimension just mentioned is of course that between the walls 30 and 3|.

When tubes containing expansion bulbs are to be made, the method comprises substantially the same steps as those above-described, except that the expansion bulb or bulbs are first blown into the tubing, either in the outer tube as shown at 32 in Fig. 5, or in the inner tube as shown at 33 in Fig. 6, or in both tubes, as will be readily understood without further need for specific illustration. Fig. 7 illustrates a similar tube. in which the inner tube has two bulbs spaced apart, being disposed near the ends of the double walled tube. It will be readily understood that by such a structure provision is made for compensatory adjustments to relieve internal tensions set up in one or the other tube, or in both, as the result of differences in temperature within the channel C as against the atmospheric temperature to which the outer tube is subjected.

Any suitable glass may be used in carrying the above method into practice, for which purpose a borosilicate glass has been found satisfactory.

The invention may be utilized not only for making straight jacketed tubes, but also may be embodied in many other shapes, of which a few examples will now be described. v

In Figs; 8 and 9 isillustrated an adaptation of the method as employed in making L-shaped jacketed tubes, or Ls" as they are sometimes termed. A satisfactory procedure is to make the inner L-shaped tube designated by the reference .character 40, having one end, as 42, formed with a closed bulb, while the end of the branch 4I of the L is open, .just as in the case of the open end 23 of the straight tube shown in Fig. 1. Indeed the parts 40, 4|, 42, and 43 of the L-shaped tube shown in Fig. 8' may be considered as illustrative of the parts numbered 20, 2|, 22, and 23 in Fig. 1.

Furthermore, as in Fig. 2 the numeral 23 designates theclosed end of the tube after'an outer tube 24 has been secured thereto in the manner described above, so in Fig. Sthe numeral '43 designates the closed end common to the inner tube 4| and the outer. tube 44.

In order to complete the jacketing of the L along the stretch designated 40 in Fig.8, a separately formed outer tube section designated 45 in Fig. 9 is superimposed upon the part 40 of the tube shown in' Fig. 8 and a beveled fused joint is first formed at 46 between suitably beveled edges at the meetingends of the outer tube sections 44 .and 45; then, just as shown in Figs. 2 and 3, a

joint 41 is made between the outer ends of tubes 40 and 45. This end joint is finished oil! by removal of the superfluous tip 48, and the end 49 of the resultant product resembles that indicated at 29 in Fig. 4. v

This method of making the L-shaped tube, illustrated in Figs. 8 and 9, has the common characteristic with respect to the method of making the straight tube shown in Fig. 4, that one end of the double walls by which the jacket is formed can be finished ofl prior to evacuation, and that another joint, spaced at any desired and suitable distance from the first joint, can be made during or after evacuation of the intra-mural space, this final joint being made by means of the contractile effect resulting from the circumambient atmospheric pressure, which becomes eflective when the glass of the adjacent wall portions is heated sufliciently to promote fusion at the annular contiguous ends. Thus the L-shaped member is provided with a vacuum jacket, coextensive with its length, and regardless of its shape.

By a further adaptation of the same principle, numerous other-shapes can be made, and it is not always necessary for the outer jacket tube to correspond exactly in shape with the inner one. For example, an inner spiral tube may be made with a straight outer jacket, as illustrated in Figs. 10, 11,' and 12. In Fig. 10 the spiral inner tube designated 50 is first made, having at one end a portion 5| closed by a bulb 52, the latter corresponding to the bulb 22 at the end of the straight portion 2| in the tube of Fig. 1. During this first stage, the other end of the spiral has a straight open portion 53 corresponding to the straight open end 23 of the tube shown in Fig. 1. During the next stage, a tube 54 of suitable diameter is slipped over the spiral portion of the inner tube 50 and a joint is made at the end 53 correspondingto the similar joint at 23 between the tubes 20 and 24 of Fig. 2. Then the'other end of tube 54 is drawn down as at 55 into proximity with the bulb 52, and is drawn down still further at 56 toreceive a rubber or other evacuating means or coupling (not shown).

The remaining stages in the formation of a shape of this kind consist in completing the annular fused joint at 51 by a softening of the adjacent double walls at that region'and so permitting atmospheric pressure to force the walls together, after which the superfluous tip parts 58 are removed, according to usual glass-blowers practice and the end 59 is finished up if necessary by further fusion and smoothing to be symmetrical with the end 53.

It will be seen from the foregoing that the final product in each of the examples above described presents a very practical, sturdy, inexpensive and efficient embodiment of my invention, and that these examples, which are merely illustrative, serve to teach the novel application of a natural principle in practice of the improved method of forming jacketed double walled tubes or other shapes herein disclosed. As already indicated, the examples given are merely illustrative and are not intended to exclude similar adaptations in as many other forms or shapes as may embody the idea of means constituting the generic feature of the present invention.

For example, as already indicated briefly at an earlier point in this disclosure, I have found in practice that it is not only possible, but often desirable, to make a seal of a preliminary nature at the region indicated by the reference charactr 26 in Fig. 2, and by 56 in Fig; 10, thus leaving this end of the tube ready for the sealing of the annular ring at the region indicated by the reference character 25 in Fig. 2, and by 55 in Fig. 10.

There is a vacuum in the annular space at the region 25, or 55 as the case may be, or in any equivalent embodiment of the novel structure represented by these illustrative examples, and by properly heating around the designated regions 25 or 55, the existing vacuum tends to collapse the two tubes together at that region.

This last-described method is the now-preferred method, in that the tube can be manipulated more readily during the diflicult step of completing the annular seal if the tube is not attached to a pump,and the presence of the preliminary seal at the-region 26 permits detachment of'the tube from the pump while preserving the tube in a state in which the vacuumengendered contractile bias is eifective at the annular region where the'flnal seal is to be made, viz., at 25,- 55 or the like.

It is noteworthy-that the tube-illustrated in Fig. 3 represents not only a tube constituting an incomplete product, when regarded from the aspect of the flanl product which constitutes the objective of theentire method, carried through to the stageillustrated' in Fig. 4, etc., but the tube of Fig. 3' constitutes an entity having distinctive characteristics which are desirable for particular uses; for example, if avacuumjacketed tube is required which is closed at one end. I

Similarly; the tube of Fig. 2, when the preliminary seal at region 26 hasbeen made, as already described, andwhen the tube, inthis condition, has been removed from the evacuator means, clearly constitutes an entity which in itself is anew article of manufacture, viz., an in tegral blank or intermediate product," of which any desired number may be made and accumulated preparatory to the performance ofthe final step or stepswhich result in the product of Fig. 3 and then of Fig.4, or any suitable modification thereof. f j

Such blanks will also be foimd susceptible of usual employment otherwise, so that the invention lends itself to mass production of such tubes in which the earlier steps of the method yield an intermediate product which is not essentially limited to completion by' the remaining steps of the preferred method if a final product is required for other uses than the principal intended uses herein exemplified.

A few embodiments of the novel jacketed tubes in combination with apparatus of a nature especially requiring the use of such tubes are shown in Figs. 13, 14 and 15.

In Fig. 13, a tube, identical info mation with that of Fig. 4, but somewhat shorter, is illustrated for use as a vacuum jacketed sight glass at the outlet of a condenser C, the latter being shown in diagrammatic, fragmentary form, as are also the elbow c and the conduit a leading from the condenser. The tube embodying the invention is designated in this instance by the reference character T, and its ends 23 and 29 are embraced between cup-shaped seats 0, and 0 provided in the elbow c and the conduit 0, respectively. The reference characters H and 62 designate packing means of known form.

In Fig. 14 is shown a tube Ti, which may be regarded as in all respects identical with the tube shown in Fig. 4. It is mounted as a gauge glass for a storage tank C containing liquids distilled to temperatures below 10 C. The mountings M and M are of usual structure, embodying valves V and V, and the reference character 63 designates the usual strengthening rods connecting the mountings M and M. The reference character P designates a pet cock.

In Fig. 15 is illustrated a series of vacuum jacketed, transparent glass tubes each embodying my invention and combined in a system for conveying fiuids. If liquids of low temperatures are to be conducted through the system, the different components are respectively adapted to permit the contents to remain visible by preventing frosting due to the accumulation of moisture deposited from the atmosphere. In this figure the reference character C2 designates a storage tank having a suitable stumng box 8 of ordinary structure, which does not require description, and in which is seated one end, as 23, of a tube identical in construction and shape with that of the tube 24 in Fig. 4, being designated-therefore by that reference character.

The other end 29 of this tube is seated within a spigot 3 formed at one end of an L-shaped member 10 which is identical in construction with the L-shaped member shown in Fig. 9, except that in Fig. 15 the L-shaped member is formed with the said spigot by the exact method of procedure described in full with reference to the L-shaped member shown in Figs. 8 and 9. The remaining component of the series shown in Fig. 15 is a member 1| having a spigot s' with reference to which the remarks above as to the spigot s apply in every respect.

It will be readily understood. that the series of tubes shown in Fig. 15, "or any equivalent assembly of similar components embodying my invention, can be extended indefinitely, and every such extension, with all possible implications as to variations in form, and adaptations to meet the needs of particular installations,falls within the purview of the present invention.

Although I have particularly described a specific embodiment of my invention and explained the principle, construction, and mode of operation thereof, nevertheless, I desire to have it understood that the form selected is merely illustrative and does not exhaust the possible physical embodiments of the idea .of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. l'he-method of fabricating a vacuum-jacketed glass shape, said method comprising the step of assembling an outer glass wall with an inner glass wall; the step of fusing said walls together at a selected region and so forming there a sealed joint; the step of heating the outer wall and drawing it into proximity to the inner wall ata region spaced from said first-named joint; the step of evacuating the jacket space enclosed between said walls intermediate said regions; and the step of fusing said walls together at said last-named region, utilizing the contractile force produced by said vacuum to make a sealed joint at said last-named region.

2. The method of fabricating a vacuum-jacketed'glass tube; said method comprising the step of assembling an outer glass tube with an inner glass tube; the step offusing together adjacent walls of said tubes at a selected region to make a sealed joint of substantially annular shape; the step of evacuating the jacket space between said walls and concurrently fusing together said walls at a region spaced from said first-named joint, utilizing the vacuum in said jacket space to produce a contractile sealing efiect at the locus of the last-named joint.

3. The method of fabricating vacuum-jacketed double-walled glass shapes which comprises the step of forming out of fusible material, such as glass, a shape adapted to serve as the inner wall of a vessel, conduit or vehicle for the storage or transfer of fluids, the step of forming out of fine at least a portion of said inner wall, and

thereby to serve as the outer wall of the jacketed final shape; the step of fusing together said walls at a suitable region: the step of bringing together at a remote region other portions of. said inner and outer walls, and forming a hollow evacuation tip at said latter region; the step of evacuating the intramural jacket space; and the step of heating said adjacent wall-portions to the fusion point whereby atmospheric pressure is permitted to become effective to exert a contractile force on said adjacent wall portions, bringing them into fused, sealing contact.

4. The method of fabricating vacuum-jacketed double-walled glass shapes which comprises the step of forming out of fusible material, .such as glass, a shape adapted to serve as the inner wall of a vessel, conduit or vehicle for the storage or transfer of fluids, the 'step of forming out of simto serve as the outer wall of the jacketed final shape; the step of fusing together said walls at a suitable region; the step of bringing together at a remote region other portions of said inner and outer walls, and forming a hollow evacuation tip at said latter region; the step of evacuating the intramural jacket space; and the step of heating said adjacent wall-portions to the fusion point, whereby atmospheric pressure is permitted to become efiective to exert a contractile force on said adjacent wall portions, bringing them into fused, sealing contact and the step of removing said tip from said last-named joint formed after evacuation.

.5. The method of fabricating vacuum-jacketed double-walled glass shapes which comprises the step of forming out of fusible material. such as glass, a shape'adapted to serve as the inner wall of a vessel, conduit or vehicle for the storage or,

transfer of fiulds, the step of forming out of similar fusible material a shape adapted to confine at least a portion of said inner wall, and thereby to serve as the outer wall of the jacketed final shape; the step of fusing together'said walls at a suitable region; the step of bringing together at a remote regio'n other portions of said inner and outer walls, and forming a hollow evacuation tip at said latter region; the step of evacuating the intramural jacket space; and the step of heating said adjacent wall-portions to the fusion point, whereby atmospheric pressure is permitted to become effective to exert a contractile force on said adiacent wall portions, bringing them into fused, sealing contact and the step of removingsaid tip from said lastnamed joint formed after evacuation; and the step of finishing said last-named joint into a tipless form symmetrical with the joint formed before evacuation.

6. As a new article of manufacture, vacuumjacketed, glass tubing comprising an inner wall and an, outer wall, said inner wall surrounding any extended channel and being formed with one or more bulbous enlargements intermediate the length of the channel to permit compensation for unequal expansion as between said walls, while preserving the channel undiminished in diameter.

'1. As a new article of manufacture. a generally straight vacuum-jacketed glass tubing unit comprising an inner wall and a parallel outer wall, one of said walls being formed with one or more bulbous enlargements to permit compensation for unequal expansion as between said walls, while 76 preserving a straight channel of undiminished diameter through the axial space defined by said inner wall.

8. The method of fabricating a vacuum-jacketed glass shape, said method comprising the step of assembling an outer glass wall with an inner glass wall; the step of fusing said walls together at a selected region and so forming there a sealed joint; the step of heating the outer wall and drawing it into proximtiy to the inner wall at a region spaced from said first-named joint; the step of evacuating the jacket space enclosed between said walls intermediate said regions; the step of making a preliminary seal in said outer tube between said second-named region and the evacuating means, and removing said tube structure from said evacuating means; and the step 01' fusing said walls together at said second-named region. utilizing the contractilev force produced by said vacuum to make a sealed joint at said second-named region.

9. As a new article of manufacture, a generally straight vacuum jacketed glass tube unit, comprising an inner wall formed by an open ended straight wall inner glass tube and a substantially parallel outer wall formed by an outer glass tube, the adjacent ends of the walls of the tubes being joined and integral with each other, thereby forming a straight open ended channel of undiminished diameter throughout the axial space defined by said inner tube, and a vacuum jacket surrounding said channel and formed by both said tubes, said vacuum jacketed glass tube also having means serving to compensate for unequal expansion as between said walls.

NATHANIEL M. ELIAS. 

